Yucca plant help.

Hello everyone,
So I have a Yucca elephantipes that is in trouble. It has started weeping a dark stick from the main trunk (stem?) Is is also gone soft and the shoots have started to fall off. At first I though it was root rot, but I have taken it out and can not see any issue with the roots however I'm no expert, the smaller of the three trunks separated from the main two when I pulled it out, it appears to be back and almost hollow inside.
Does anyone know if this is able to be rescued or is it a lost cause, I've had it for three years now and have never had any issues with it and have not changed its position or water routine.

 

It looks like one stem has not rooted and has been slowly rotting instead.

Put the others, with roots, back in some fresh compost and discard the rotten one.